Production of photographic images or printing plates utilizing polyimides

ABSTRACT

PROCESS FOR THE PRODUCTION OF PHOTOGRAPHIC IMAGES OR PRINTING FORMS USING LIGHT SENSITIVE LAYERS WHICH ARE FREE FROM SILVER HALIDE AND CONTAIN CYCLIC POLYAMIDES ACCORDING TO GERMAN PATENT (P 15 22 385.5) WHEREIN THE PHOTOGRAPHIC MATERIAL IS IMAGEWISE EXPOSED AND HEATED TO A TEMPERATURE OF BETWEEN 100*C. AND 200*C. AND THEN IS UNIFORMLY EXPOSED. THE PROCESS IS BASED ON THE FINDING THAT THE COLOURED RADICAL IMAGE SUBSTANCE FORMED BY IMAGEWISE EXPOSURE IS IRREVERSIBLY CONVERTED INTO COLOURLESS OR ALMOST COLOURLESS COMPOUNDS BY HEATING THEM TO 100*C. TO 200*C.

United States Patent 3,694,208 PRODUCTION OF PHOTOGRAPHIC IMAGES ORPRINTING PLATES UTILIZING POLYIMIDES Erwin Ranz, Harald von Rintelen,Heinz-Dieter Schutz,

Gerhard Muller, and Wolfram Neumann, Leverkusen,

Germany, assignors to Agfa-Gevaert Aktiengesellschaft, Leverkusen,Germany No Drawing. Filed Oct. 30, 1970, Ser. No. 85,811

Claims priority, application Germany, Nov. 6, 1969,

P 19 55 751.8 Int. Cl. G03c 3/24 US. CI. 96-48 HD 5 Claims ABSTRACT OFTHE DISCLOSURE Process for the production of photographic images orprinting forms using light sensitive layers which are free from silverhalide and contain cyclic polyamides according to German patent (P 22385.5) wherein the photographic material is .imagewise exposed andheated to a temperature of between 100 C. and 200 C. and then isuniformly exposed. The process is based on the finding that the colouredradical image substance formed by imagewise exposure is irreversiblyconverted into colourless or almost colourless compounds by heating themto 100 C. to 200 C.

The invention relates to a process for the production of photographicimages or printing forms using light sensitive layers which are freefrom silver halide and contain cyclic polyimides.

Photographic materials are known which contain as light sensitivecompounds cyclic naphthalene carboxylic acid diimides.

These compounds very rapidly become dark on exposure to light,especially to UV light, and so provide a very simple method of obtainingphotographic images by a completely dry process. Photographic materialsof this type have been described in US. Pat. specification 3,533,798.

To produce stable photographic images, it is necessary to fix thephotographic images which are obtained by rendering the light sensitivecyclic polyimides insensitive to light in the unexposed areas of thelayer. This is to be achieved e.g. by the action of reagents which reactwith unsaturated double bonds or have for example a ring opening effecton cyclopropane rings. Reagents which react with unsaturated doublebonds are among others halogens such as bromine, chlorine or iodine,halogen hydroacids such as hydrogen chloride or hydrogen bromide, ozone,peroxy acids or hydrogen, sulphenyl chlorides or sulphur dichloride andpotassium permanganate. Conversion of the light sensitive cyclicpolyimides into compounds which are insensitive to light can also beachieved by degrading the imido group, e.g. by hydrolysis into polyamidocarboxylic acid or by aminolysis into polyamides. Separation of thelight sensitive cyclic polyimides into exposed and unexposed portionscan also be achieved by selectively dissolving out the one componentwith suitable solvents.

Negative images of the original are obtained by this process.stabilising the images obtained on exposure of such photographicmaterials is a relatively complicated process. Moreover, it is notpossible to produce reversal images by the process described above.

It is an object of the invention to provide a simple method ofstabilising photographic materials containing cyclic naphthalenecarboxylic acid diimides and to modify the process hitherto known sothat direct positive images can be produced.

3,694,208 Patented Sept. 26, 1972 We now have found a process for theproduction of photographic images by exposing and stabilising a lightsensitive photographic layer which contains as light sensitive compounda cyclic polyimide of the formula in which R is a 2n-valent mononuclearor polynuclear condensed aromatic radical, e.g., a radical of thephenylene, naphthylene or perylene series, preferably a phenyl ornaphthyl radical, which may be substituted, e.g. with an alkyl radical,in particular an alkyl having up to 5 carbon atoms such as methyl, ethylor propyl, with halogen such as chlorine or bromine, nitrile or alkoxy,in particular alkoxy having up to 5 carbon atoms, and the like;

R' is an olefinically unsaturated linear or cyclic radical,

in particular an unsaturated aliphatic radical containing up to 8 carbonatoms, e.g. allyl, butenyl or pentenyl, cyclohexenyl or cyclopentenyl ora dihydropyran radical, the cyclic radicals being attached to thenitrogen atom either directly or through an alkylene bridge having up to3 carbon atoms; R may also represent S-membered or 6-membered ringswhich contain a cyclopropane group and which preferably have anendomethylene structure, e.g. a ring of the tricyclene series;

n represents 2 or 3, preferably 2;

in which the photographic material is imagewise exposed and heated to atemperature of between C. and 200 C. and then is uniformly exposed.

The process according to the invention is based on the finding that thecoloured radical image substance formed by imagewise exposure isirreversibly converted into colourless or almost colourless compounds byheating them to 100 C. to 200 C. The following compounds exhibitparticular utility:

lCO 0-C4H9 oCt-OCO H000 CO-NH HNCO -COOH -@r N I N I l H H l I VII 0 O fK33 M ed QW The light sensitive cyclic aryl polyirnides in the unexposedareas of the layer are not influenced by this heating. The lightsensitive substance in the areas which have not previously been exposedis then coloured dark by a uniform after-exposure to actinic light,preferably UV light. Since the areas which were originally exposed arenow pale, a direct positive image of the original is obtained. Thereversal images obtained in this way are stable in ordinary daylight.

The light-sensitive cyclic aryl polyimides and their open chain primaryproducts which are not sensitive to light are suitable for the processaccording to the invention. These primary products can be converted intothe light 4 sensitive compounds by a certain preliminary treatment asdescribed in the US. Pat. specification 3,533,798.

The process according to the invention may also be used for suchphotographic materials of the above US. Pat. specification which containas accelerator for the conversion reaction an isourea derivative of theformula in which R is alkyl, cycloalkyl or aryl, R is hydrogen or R, Ris alkyl with up to 5 carbon atoms and R is R.

For the preparation of the light sensitive compound, the methods givenin US. Pat. specification 3,533,798 for production of the layers andprocessing are applicable.

The process according to the invention can be used for producing offsetfoils which can be processed dry because the physical properties of thelayer are altered imagewise by heating the imagewise exposed material toa temperature of between about 100 C. and 200 C. and then uniformlyexposing the material to ultraviolet light. Even with the naked eye itcan be seen that after the subsequent exposure with ultraviolet light,the areas of imagewise exposure are highly glossy and the other parts ofthe layer are matt. In addition, the wetting properties have beenaltered in that the glossy areas which have been exposed imagewise havebecome hydrophobic and readily take up fatty printing dyes. The otherareas of the layer are more hydrophilic and repel printing dyes. Theimages produced by this method can therefore be used immediately asprinting forms for offset printing.

The differences in the wetting properties can be still further increasedby additional measures. Thus, the light sensitive substances, with orwithout binder, may be applied to a strongly hydrophilic layer supportsuch as suitably coated paper. After the layer has been heated and thenexposed to UV light, the parts of the layer which are alreadyhydrophilic can easily be removed by rubbing with a moist cloth orsponge, thereby exposing the highly hydrophilic surface of the layersupport. Surprisingly, the imagewise exposed parts of the layer adheremuch more firmly to the support and are therefore not removed byrubbing. These effects can be reinforced as desired by suitablymodifying the light sensitive layers. The offset foils produced in thisway can be used for the offset process in the usual manner.

EXAMPLE 1 Preparation of the light sensitive layer 5 g. of Compound VIdissolved in 300 ml. of chloroform are mixed with 200 ml. of a 20%polyvinylacetate solution in chloroform, applied to a paper support anddried.

Processing-The layer is exposed to a mercury vapour lamp Osram HQA (400watt) behind a continuous tone original (silver image). Exposure time is30 seconds to 1 minute at a distance of 30 cm. A dark positive image ofthe original with excellent reproduction of the continuous tones isobtained.

Similar results are obtained, for example, when using Compound I in thesame way.

The picture is then heated in a heating cupboard at 200 C. for secondseither immediately or at any time after exposure. The colour of theradical image substance disappears almost completely on heating. Duringthe subsequent after exposure to diffuse light (30 seconds, 30 cm.distance) from the mercury vapour lamp used for the imagewise exposure,the coloured radical image substance appears in those areas of thesample which were not exposed during the imagewise exposure. Theimagewise exposed areas which had become pale as a result of the heatingto 200 C. are not changed during the subsequent diffuse exposure.

A high contrast reversal image which is stable in daylight is obtained.

EXAMPLE 2 A high contrast reversal image which is stable in dayon ahydrophilic paper support. It is exposed imagewise to a UV lamp asdescribed in Example 1. It is then heated at 200 C. for 2 minutes. Aftersubsequent diffuse exposure to UV or daylight, the image areas arehighly glossy and the surroundings are matt. By gently rubbing with awad of cotton wool steeped in alcohol, the binder is completely removedfrom those areas (matt) which were not exposed imagewise.

When this layer is used as master in an oifset printing apparatus, oildye is taken up by those areas which are relatively hydrophobic. Offsetprints of high quality are obtained.

What we claim is:

1. The production of photographic images by imagewise exposing a layerof supported light sensitive material which comprises a light sensitivepolyimide of the formula ll R NR' in which R is a 2nvalent, mononuclearor polynuclear aromatic radical; R is either (1) an olefinicallyunsaturated linear aliphatic radical, (2) an olefinically unsaturatedcyclic aliphatic radical linked to the nitrogen either directly orthrough an alkylene chain or (3) a 5 or 6 membered ring which comprisesa cyclopropane grouping and n is 2 or 3, t for the production of animage of a colored radical image of a colored radical image substance,heating the exposed layer to a temperature in the range of 100-200 C. toconvert in the imagewise exposed areas the colored radical imagesubstance to a substantially colorless light-insensitive compound anduniformly exposing said treated layer to form a positive photographicimage by coloring said light sensitive polyimide. 2. A process for theproduction of printing forms for offset printing which comprisesimagewise exposure of a photographic photosensitive hydrophillic layeron a support comprising a light sensitive polyimide of the formula 0 itB N-R ll in which R is a 2n-valent, mononuclear or polynuclear aromaticradical;

R is either (1) an olefinically unsaturated linear aliphatic radical,(2) an olefinically unsaturated cyclic aliphatic radical linked to thenitrogen either directly or through an alkylene chain or (3) a 5 or 6membered ring which comprises a cyclopropane grouping and n is 2 or 3,forming a colored radical image substance in said hydrophillic layer bysaid imagewise exposure, heating the hydrophillic layer to a temperaturebetween and 200 C. to convert the image substance to a substantiallycolorless light insensitive compound, and uniformly exposing the treatedlayer to produce hydrophobic imagewise exposed areas and the remainingareas of said printing form being less hydrophobic. 3. A printing formfor offset printing produced in accordance with the process of claim 2.

4. A process as claimed in claim 1 in which R is an olefinicallyunsaturated cyclic radical.

5. A process as claimed in claim 1 in which the polyimide used is one ofthe compounds of Formulae I to XIV illustrated herein.

References Cited UNITED STATES PATENTS 3,533,798 10/1970 Muller et al96-90 OTHER REFERENCES Advanced Organic Chemistry by Fieser and Fieser,Reinhold Publishing Co. New York, 1965 at page 24.

NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR. Assistant ExaminerUS. Cl. X.R. 96-90, 33

